There are two sections.... The roof and gutter are one pressed panel which is spot welded to the side panel... The rail where the headlining strip is welded on is part of the side panel. Easiest way is to find a van at a wreckers and cut a good section of roof and gutter out of it... Unless you are good at shaping sheet steel....

It's not that hard a job if it's only a small rust section, a lot harder if it's a large section along the gutter.